1. Field of the Invention
The present invention relates to a zoom camera that uses a zoom lens for photography and has a pseudo zooming function by which a photo print contains a virtually magnified subject compared to the original frame photographed through the zoom camera, so the photo print looks like being photographed at a longer focal length than an actual focal length of the taking lens actually used for photographing the original frame.
2. Background Arts
In standard photo-printing, a substantially whole area of an individual frame photographed on a photo filmstrip is printed at a standard magnification to provide a photo-print of a constant size. On the contrary, in a pseudo zooming print system, that is disclosed for example in JPA 3-92838, JPA 4-27927 and JPA 4-317035, a partial area to print within an original frame is defined by trimming or masking four sides of the original frame, and a photo-print of the constant size is made from the defined partial area by printing at a larger magnification than the standard magnification. As a result, the photo-print contains only those subjects included the partial area but which are enlarged as if they were taken at a larger focal length than the actual one. This is called "pseudo zooming effect". Hereinafter, the ratio of a magnification used for the pseudo zoom printing to the standard print magnification is referred to as the pseudo zoom ratio. In other words, the focal length that is virtually obtained by the pseudo zooming is larger than the actual focal length by the pseudo zoom ratio.
In the above prior arts, data indicating whether the pseudo zooming print is designated or not, data of the area to print, or data of a selected pseudo zoom ratio is recorded magnetically on the filmstrip in association with respective frames.
JPA 4-27927 and JPA 4-317035 disclose a zoom camera that uses a zoom lens for photography and also has the pseudo zooming function. By using the pseudo zooming function in combination with the zoom lens, a zoom ratio that is larger than a maximum zoom ratio of the zoom lens is obtained in view of the subsequent photo-prints. In other words, the camera of these prior arts virtually has a larger maximum zoom ratio than an actual maximum zoom ratio of the taking lens. Therefore, the zoom lens itself may be comparatively small or cheap.
Also, JPA 4-322231 discloses a zoom camera, wherein an image magnification is automatically determined depending upon a subject distance measured by the camera. According to the determined image magnification, a focal length of the taking lens is changed, and a pseudo zoom ratio is determined depending upon the focal length. To show a virtual photographic field that will be contained in a photo-print obtained by the pseudo zooming print method, the camera of this prior art uses movable relaying lenses for a finder optical system, so as to change the focal length of the finder optical system in correspondence with the pseudo zoom ratio besides the change in the focal length of the taking lens. A mirror is used for splitting the light passing through the taking lens and directing it toward the finder optical system. In this way, a field of view that approximately corresponds to the virtual photographic field.
However, in the camera disclosed in JPA 4-27927, the photographer must choose whether to use the pseudo zooming function or not after zooming up to a telephoto terminal. Therefore, for those who do not well know the pseudo zooming function, the function is not easy to handle, especially where there are several options in the pseudo zoom ratio.
The camera disclosed in JPA 4-317035 automatically switches over the pseudo zoom ratio from 1.0 to a larger value, e.g. 1.7 when the photographer zooms up further to a telephoto side after the taking lens actually reaches its maximum focal length. Thereafter, as the photographer zooms down to a wide-angle side, the focal length of the taking lens is decreased while maintaining the pseudo zoom ratio at the larger value. When the photographer zooms down further to the wide-angle side after the taking lens actually reaches its minimum focal length, the pseudo zoom ratio is reset to 1.0. While the taking lens is zoomed in this way, the virtual photographic field is changed correspondingly.
Although the pseudo zooming function is automatically selected in this prior art, the image magnification can changed only one increment for the pseudo zooming after the taking lens is zoomed up to the maximum focal length, so that the magnification change for the pseudo zooming looks abrupt. Since the change in virtual focal length, which is determined by the actual focal length of the taking lens and the pseudo zoom ratio, is not linear, the change in the virtual photographic field and thus the virtual field of view can not change continuously.
It is possible to make the one increment small, but the effect of pseudo zooming is reduced. Moreover, in order to cancel the pseudo zooming function, the photographer needs to zoom down beyond the minimum focal length. This makes the zooming operation inconvenient. Providing several steps of increments in the pseudo zoom ratio makes the switching to or from the pseudo zooming function more complicated.
Furthermore, it is well known in the art that image quality of photographic frames tends to be lowered with the increase in the focal length of the taking lens. Besides that, since a larger print magnification is used for the pseudo zooming print system, image quality of pseudo zooming photo-prints made through the pseudo zooming print system is still more lowered, especially when a large pseudo zoom ratio of 1.7 or more is used. Accordingly, it is desirable to avoid a large pseudo zoom ratio as far as possible for the interest of print quality.
In the zoom camera disclosed in JPA 4-322231, since the pseudo zooming function is always adopted throughout the entire focal length range, and the relationship between the pseudo zoom ratio and the image magnification of the viewfinder is not considered, the print quality is unnecessarily deteriorated. Since the image magnification is automatically determined depending upon the subject distance, the photographer cannot choose an appropriate zooming position. This camera uses a motor for zooming the taking lens and a second motor for zooming the finder optical system, so that the camera is relatively large and expensive.
It is well known in the art to make a print at a different print format or aspect ratio from an original frame. To make a panoramic print, for instance, top and bottom sides of the original frame are trimmed or masked to define an elongated printing area, and the printing area is printed at a larger magnification than the standard print magnification, i.e. about 1.7 times the standard print magnification. For this printing system, data about the designated print format is recorded by the camera side optically or magnetically on the filmstrip.
JPB 5-82921 discloses a zoom camera that has the pseudo zooming function and is also able to select one of different print formats. In this camera, the field of view may be limited correspondingly to the designated print format, but the image magnification of the view finder is not changed in a pseudo zooming range, but only the boundary of the view field is limited according to the pseudo zoom ratio. Therefore, it is not easy for the photographer to imagine how the consequent pseudo zooming print would look.